The present invention relates to an automatic transmission system having a clutch and a gear transmission in which the operation for shifting gears is electronically controlled in accordance with shift map data.
In the prior art, to realize automization of the operation for shifting gears in the conventional transmission system having a clutch, such as a friction clutch, and a gear transmission, there has been proposed an electronically controlled transmission system in which actuators are associated with the clutch and the gear transmission, respectively, and the actuators are controlled by control signals issued from an electronic control device. In this kind of conventional electronically controlled automatic transmission system, the electronic control device has shift map data for determining the optimum gear position and the appropriate gear position at each instant is determined in response to the conditions of operation of an internal combustion engine associated with the gear transmission in accordance with the shift map data.
In general, there are a plurality of sets of shift map data, each set corresponding to a given position of a selector, so that the optimum gear position can be determined in accordance with the set of shift map data corresponding to the position of the selector selected by the driver at that time.
Therefore, when the selecting lever of the gear selector is changed, the gear of the transmission is subject to being shifted first to another position immediately after the selecting lever has been changed, and then shortly thereafter to a further position. That is, the automatic transmission is liable to carry out a gear shifting operation two times just after the selecting lever of the selector is changed. In the case where the transmission system is used in a passenger vehicle powered by an internal combustion engine, the passenger may receive an uncomfortable shock at this time. Furthermore, when the gear is shifted up or down just after the position of the selector is changed, it sometimes becomes difficult to obtain the required rotation torque from the output shaft of the gear transmission.